Subway Construction Milestone

Latest Tunnel Boring Technology Minimized Ground Settlement, Above Ground Disruptions

The Los Angeles County Metropolitan Transportation Authority (Metro) today announced that it has successfully completed tunneling for the D Line Subway Extension Project that will connect downtown L.A. with West L.A.

This major construction milestone was accomplished safely in one of the densest and most geologically challenging urban corridors in the L.A. region and nation.

“This safe completion of tunneling through this part of Los Angeles is a milestone in Metro’s work to expand fast and reliable public transit across the region,” said Karen Bass, L.A. City Mayor and Metro Board Chair. “When completed, the D Line extension will make Metro transit available to 53,300 more weekday riders traveling between Downtown Los Angeles and the Westside. Thank you to all of the construction workers who have given their time and talent to successfully complete the tunneling.”

With the completion of tunneling, Metro will continue to work with its two contractors as a part of a joint venture with Skanska-Traylor-Shea and Tutor-Perini/O&G to complete seven new underground stations in Section 1 between Wilshire/Western and Wilshire/La Cienega, Section 2 between Wilshire/La Cienega and Century City, and Section 3 between Century City and Westwood.

Contractors utilized the latest Tunnel Boring Machine (TBM) technology to excavate approximately 40-60 feet per day to help complete tunneling for the project. The 400 foot-long, 21 foot-diameter earth digging machines utilized closed face, pressurized TBM technology that minimizes ground settlement during excavation. The machines also lined the tunnel itself with precast concrete segments that were bolted together to form secure rings making them water- and gas-tight, preventing water and gas-related risks. This same TBM technology was successfully employed on Metro’s 2009 Eastside Extension Project.

“The D Line Subway Extension is one of the most complex engineering feats that Metro has undertaken,” said Lindsey Horvath, Chair of the LA County Board of Supervisors and Metro Board Member. “Its complexity is matched by the immense value the project will bring to Los Angeles when it opens and carries 30,000 daily riders through one of our densest and most job-rich regions.”

During its five years of tunneling, Metro faced and successfully overcame many technical challenges like gassy ground, tar sands and abandoned oil wells. Near the La Brea Tarpits, for example, Metro’s advanced TBMs made their way through tar sands, and used horizontal directional drillings to probe the earth so contractors could identify and remove potential objects before any TBM damage occurred. Metro also safely used the same methods to identify and avoid unmapped and abandoned oil wells underneath Beverly Hills High School.

“Congratulations to Metro and its contractors for reaching a critical milestone for the D Line Subway Extension,” said L.A. County Supervisor and Metro Board Member Holly J. Mitchell. “We are one major step closer to a Los Angeles where everyone has access to all the cultural and economic resources the region has to offer.”

“Now that tunneling is complete, it won’t be long before Metro completes this mega-project and makes it possible for everyone to travel from downtown L.A. to West L.A. in under 30 minutes,” said Katy Yaroslavsky, L.A. City Council Member and Metro Board Member. “This subway extension will catalyze ridership on the entire Metro System in the years ahead, bringing many thousands of new riders throughout Metro’s transit system.”

“The end of tunneling work on this project is a triumph of engineering, planning and execution. Our construction team undertook a painstaking process that helped us keep everyone in these communities safe and deliver a better project for the people of L.A. County,” said Stephanie Wiggins, Metro CEO. “We have proven yet again our capability to safely tunnel underneath a range of different structures as well as sensitive and historic sites.”

Forecasted openings are 2025 for Section 1, 2026 for Section 2 and 2027 for Section 3 of the project.

Metro secured local funding to build the project via the 2008 Measure R and 2016 Measure M voter-approved transportation sales tax measures. These local funding sources were then matched by federal funding, which ultimately amounted to approximately half of the project’s overall cost.

About Metro
The Los Angeles County Metropolitan Transportation Authority (Metro) is building the most ambitious transportation infrastructure program in the United States and is working to improve mobility through its Vision 2028 Plan. Metro is the lead transportation planning and funding agency for L.A. County and carries nearly 900,000 boardings daily on a fleet of 2,200 low-emission buses and six rail lines.

https://www.metro.net/about/la-metro-officially-completes-five-years-of-tunneling-adding-nine-miles-on-d-line-subway-extension-project-between-downtown-west-la/